title: Visualization of the hybrid state of tRNA binding promoted by spontaneous ratcheting of the ribosome.
abstract: A crucial step in translation is the translocation of tRNAs through the ribosome. In the transition from one canonical site to the other, the tRNAs acquire intermediate configurations, so-called hybrid states. At this stage, the small subunit is rotated with respect to the large subunit, and the anticodon stem loops reside in the A and P sites of the small subunit, while the acceptor ends interact with the P and E sites of the large subunit. In this work, by means of cryo-EM and particle classification procedures, we visualize the hybrid state of both A/P and P/E tRNAs in an authentic factor-free ribosome complex during translocation. In addition, we show how the repositioning of the tRNAs goes hand in hand with the change in the interplay between S13, L1 stalk, L5, H68, H69, and H38 that is caused by the ratcheting of the small subunit.
authors.affiliation: Howard Hughes Medical Institute, Columbia University, 630 West 168th Street, College of Physicians and Surgeons, Black Building 2-221, New York, NY 10032, USA.
authors.forename: Xabier
authors.initials: X
authors.lastname: Agirrezabala
authors.forename: Jianlin
authors.initials: J
authors.lastname: Lei
authors.forename: Julie L
authors.initials: JL
authors.lastname: Brunelle
authors.forename: Rodrigo F
authors.initials: RF
authors.lastname: Ortiz-Meoz
authors.forename: Rachel
authors.initials: R
authors.lastname: Green
authors.forename: Joachim
authors.initials: J
authors.lastname: Frank
mesh_terms: D001665:Binding Sites; D020285:Cryoelectron Microscopy; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D010441:Peptide Chain Elongation, Translational; D014176:Protein Biosynthesis; D021122:Protein Subunits / Q000378:metabolism; D012343:RNA, Transfer / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure*; D054681:Ribosome Subunits, Large, Bacterial / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure*; D054680:Ribosome Subunits, Small, Bacterial / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure*
chemical_list: D021122:Protein Subunits; D012343:RNA, Transfer